Pico projector architecture may have two different types, transmission type and reflection type depending on the manner of image light reaching a projector display from light source. The transmission type may include high temperature poly-silicon (HTPS) and alpha-Si as light valve; the reflection type may include digital light processing (DLP) and liquid crystal on silicon (LCoS) as reflective devices. No matter which type is employed, light source used for both types may be the same.
With RGB LED light source which includes LEDs corresponding to respective colors of red, green and blue (RGB) in pico projector applications, better color performance of projection can be obtained for micro displays (e.g. light valves for transmission-type or reflective devices for reflection type). However, colors of LED light source are very sensitive to temperature and may drift with different temperatures. Therefore, LED light sources have to be well controlled over the ambient temperature to maintain the precise colors. Heat dissipation becomes very important for pico projector with RGB LED light source. Although more lighting power may be saved due to usage of LED light source, temperature control of a miniaturized projector becomes another technical issue.
Furthermore, for the projectors with LED light source, RGB LED light are constantly on, which wastes a lot of power because each LED of the light source is only used for ⅓ period.
In addition, most visible-light-communication (VLC) applications modulate the light source with very high frequency by superimposing dummy pattern to maintain lighting performance. To enhance the VLC communication speed, existing approaches are either using different wavelength (different color light of RGB) to extend the bandwidth or using multi-input multi-output (MIMO) architecture. In micro display system including of LCD, DLP, LCoS, etc., micro displays may be used to modulate the color light intensity per micro display globally.